Apparatus for developing electrophotographic plates



June 19, 1956 WALKUP ETAL. 2,750,22

APPARATUS FOR DEVELOPING ELECTROPHOTOGRAPHIC PLATES Filed Dec. 13, 1951 2 Sheets-Sheet l INVENTORS LEWIS E. WAL KUP HAROLD E. COPLEY WALTER A. BECKDAHL BY FM ATTORNEY June 19, 1956 E. WALKUP ET AL 2,750,922

Filed Dec. 15, 1951 FIG.4

INVENTORS LEWIS E. WALKUP HAROLD E. COPLEY WALTER A. BECKDAHL ATTORNEY nited ttes APPARATUS FOR DEVELOPING ELECTRO- PHOTOGRAPHIC PLATES Application December 13, 1951, Serial No. 261,532

Claims. (Cl. 118-57) This invention relates to electrocopy apparatus for making electrophotographic images and, in particular, to developing or dusting mechanism therefor.

The principal object of the invention is to afford a compact portable apparatus of simple and economical construction that can readily be operated in a small space to perform the required steps of electrophotography and specifically to perform the developing or powder dusting step.

An additional object of the invention is to provide a simple and practical form of powder-dusting mechanism which can readily be employed in conjunction with charging, exposing, and transfer mechanisms, and which can be operated to apply electroscopic powder to the electrostatic image on an electrophotographic plate and to apply cleaning powder to the plate for removing excess electroscopic powder therefrom after a transfer operation is completed, preparatory to using the plate for making another copy.

In the drawings:

Figure 1 is an isometric view of a portion of the developing apparatus of the invention, partially broken away showing the means for dusting electroscopic powder on an electrophotographic plate which is illustrated in clamped position on the powder tray;

Figure 2 is an isometric view showing a powder tray in operative position on its support with a plate clamped therein ready for dusting;

Figure 3 is a view similar to Figure 2 showing the clamping device elevated in the position assumed when a plate supporting frame is to be inserted or removed;

Figure 4 is a longitudinal, vertical section of the mechanism shown in Figure 1, taken along the line 4-4; and

Figure 5 is an isometric view of an electrophotographic plate adapted to operate with the powder tray.

This application is a continuation-in-part of our copending application Serial Number 63,922 filed December 7, 1948, and entitled Electrocopy Apparatus, now Patent No. 2,588,675, issued March 11, 1952, wherein there is described a complete and compact apparatus for the preparation of electrocopies. According to this apparatus an electrophotographic plate is sensitized by imposing an electrostatic charge substantially uniformly across its surface and is then photographically exposed to yield a plate bearing an electrostatic latent image which is capable of being developed to form a visible image by dusting with an electroscopic powder.

Dusting or developing of the electrostatic latent image or dusting of the charged photoconductive insulating surface with electroscopic powder is, according to the present invention, effected by the mechanism shown in Figures 1, 2, 3 and 4 herein, including a base 27 with trunnion bearings formed by cars 28 having grooves or notches 29 formed therein to receive trunnions 31 carried by projecting ends 41 formed on side rails or walls 32 of a tray assembly 42, within which is arranged the electroscopic dusting powder 33. Tray assembly 42 also includes end walls 43 and bottom wall 44, which are in- "ice tegrally connected with side walls 32 to form a box-like, dust-tight container, and is provided at one end with a cover portion 45 that is connected between one end wall 43 and adjacent portions of side walls 32 and is sub stantially coplanar therewith, whereby to form a covered end portion or trough 39 for containing powder 33 when the tray is rocked to a vertical position, as described below. The powder tray assembly 42 is also provided with means for clamping an electrophotographic plate assembly thereagainst, such clamping operation being effected by a frame including cross-rods 34 pivotally mounted in brackets 35 and carrying rails 36 having rubber or elastic pads 37 on their bottom edges which contact the outer surface of the plate assembly to clamp the latter against the tray, while 38 designates any convenient form of releasable catch for holding the rods 34 in their clamping position, as illustrated in Figure 1.

The structure shown in Figure 5 is an electrophotographic plate assembly of a type with which the present invention is intended to be used. The structure includes a metal conducting plate 21 that is provided with a photoconductive insulating layer or surface coating 22 and is attached to and supported by a frame or cassette 23 which optionally may be formed of wood or other suitable material. The photoconductive layer 22 faces the open side of the frame, as shown in Figure 5, and is covered or protected by a light shield 24 of any suitable stiff material that is insertable or removable through a slot 25 (see Figure l) at one end of the supporting frame 23 and into grooves or tracks 26 in the frame, the shield 24 acting when inserted therein to cover the photoconductive insulating surface 22 of the plate and protect it from light.

To effect the powder-dusting operation and form a powder image on the plate after the latter has been charged electrostatically and exposed, the plate assembly with the light shield 24 in position is placed on the powder-dusting tray assembly 42 with the photoconductive insulating surface 22 facing inwardly toward the powder 33. The clamping frame is then swung downwardly and the catches 38 engaged over the ends of rods 34 to hold the plate assembly in clamped position as shown in Figure 1. The light shield 24 is then removed and tray assembly 42 is rocked on the supporting trunnion bearings 28 by lifting the free end of the tray upwardly and swinging it over until it is in reverse position or above the supporting frame. The powder in the tray will then fall against the photoconductive insulating surface 22 of the plate, and by moving the dusting tray assembly 42 upwardly and downwardly several times, the powder 33 is caused to flow across the plate and is evenly distributed over the electrostatic image, to which it adheres. Two sets of trunnion bearings 28 preferably are provided on the base 27 to permit the use of two similar dusting trays, one tray being filled with cleaning powder of any suitable character which is used to clean the plate and remove excessive electroscopic powder after the transfer operation is completed, preparatory to using the plate for another copying operation.

In the operation of the apparatus, an electrophotographic plate assembly is charged and exposed in conventional manner and is placed on the powder dusting tray assembly 42 and clamped therein with the electrostatic image surface of the plate facing toward the interior of the tray. Located within the tray is a suitable dusting powder 33 which is applied to the surface of the plate by turning the tray upside down and rocking it back and forth to cascade the powder across the plate surface. In the beginning and conclusion of the rocking or cascading step the tray assembly 42 is held in a vertical position, as in Fig. 4, to permit the powder to collect in the covered end portion or trough 39 of the tray,

whereby the plate surface isv free from powder except that powder which is electrostatically held thereon.

7' The tray assembly 42 is then returned to its normal position with the plate assembly on top thereof and the plate is then unclamped and removed, bearing on. its surface an electroscopic powder image. corresponding to the electrostatic latent image; The elect-rophotographic plate assembly with its adherent powder image is then removed from the tray assembly 4 2, and the powder image may be transferred to a transfer material in a method such as that described in the previous referred to application Serial Number 63,922.

After utilization of the electroscopic powder image for example, by transfer to a second surface, the image or residual image is removed from the plate by positioning the plate in a powder dusting tray similar to that already described and containing a suitable. cleaning powder, which when the tray is rocked acts to remove the electroscopic powder from the plate, leaving it then ready for another copying operation.

While the invention has beendescribed with reference to the structure shown herein, it is not limited to.- the structural details set forth, and this application is. intended to cover such modifications or departures as may come within the purposes of the improvements or the scope of the following claims.

What is claimed is:

1. An apparatus for developing electrophotographic plates comprising a rectangular, box-like, open tray having a bottom and side and end Walls integrally formed to provide a dust-tight powder container, a cover por tion connected between one end wall and adjacent portions of the side walls whereby to form a covered portion of the tray at one end thereof, the upper surfaces of said cover portion and side and end walls being substantially coplanar to form a bearing surface for supporting an electrophotographic plate, clamping means mounted on the side walls of said tray for clamping an electrophotographic plate over the opening of sai'd tray, trunnions formed on the side walls of the tray, a base member, and trunnion bearings on said base member for supporting the trunnions on the tray for rotational movement.

2. An apparatus for developing electrophotographic plates comprising a rectangular, box-like, open tray having a bottom and side and end walls integrally formed to provide a dust-tight powder container, a cover portion integrally connected between one end wall and adjacent portions of the side walls whereby to forma covered portion of the tray at one end thereof, the upper surfaces of said cover portion and side and end walls being subr stantially coplanar to form a bearing surface for supporting an electrophotographic plate, clamping means mounted on the side walls of said tray for clamping an electrophotographic plate over the opening of said tray, trunnion supports formed on each of the side walls ofthe tray, a trunnion mounted on each of said trunnion supports, a base member, and trunnion hearings on said base member for supporting the trunnions for rotational movement.

3. An apparatus for developing electrophotographic plates comprising a rectangular, box-like, open tray having a bottom and side and end walls integrally formed to provide a dust-tight powder container, a cover portion integrally connected between one end' Wall and adjacent portions of the side walls whereby to form a covered portion of the tray at one end thereof, the upper surfaces of said cover portion and side and end walls being substantially coplanar to form a bearing surface for supporting an electrophotographic plate, resilient clamping means mounted on the outer surfaces of the side walls of said tray for securing an electrophotographic plate over the opening of said tray, trunnions' formed on the side walls of the tray, a base member, and trunnion. bearings on said base member for supporting the trunnions on the tray for rotational movement.

4. An apparatus for developing electrophotographic plates comprising a rectangular, box-like, open tray having a bottom and side and end walls integrally formed to provide a dust-tight powder container, a cover portion integrally connected between one end wall and adjacent portions of the side walls whereby to form a covered portion of the tray at one end thereof, the upper surfaces of said cover. portion and side and end walls being substantially coplanar to form a bearing surfacefor supporting an electrophotographic plate, clamping means mounted on the side walls ofsaid tray for clamping an electrophotographic plate over the opening of said tray, trunnions formed on the side walls of the tray, a base member, and trunnion hearings on said base member for supporting the trunnions on the tray for rotational movement.

5. An apparatus for developing electrophotographic plates comprising a rectangular, box-like, open tray having a bottom and side and end walls integrally formed to provide a dust-tight powder container, 21 cover portion integrally connected between one end wall and adjacent portions of the side walls whereby to form a covered portion of the tray at one end thereof, the upper surfaces of said cover portion and side and end walls being substantially coplanar to form a bearing surface for supporting an electrophotographic plate, resilient clamping means mounted on the outer surfaces of the side walls of said tray for securing an electrophotographic plate over the opening of said tray, trunnion supports formed on each of the, side walls of the tray, a trunnion mounted on each of said trunnion supports, a base member, and trunnion bearings on said base member for supporting the trunnions for rotational movement.

References Cited in thefile of this patent UNITED STATES PATENTS 29,418 Thompson et al July 31, 1860 360,952 Crowell Apr. 12, 1887 650,857 Murnane June 5, 1900 695,102 Griswold Mar. 11, 1902 1,547,945 Mustapich July 28, 1925 2,277,013 Carlson Mar. 17, 1942 2,297,691 Carlson Oct. 6, 1942 2,481,400 Davis Sept. 9, 1949 2,588,675 Walkup et a1. Mar. 11, 1952 2,600,580 Sabel et a1. June 17, 1952 

